Hi. The following is a quote of the mail that just got out to the Gentoo-Dev MailingList announcing the changes we've made and are making to better support PHP on Gentoo.
This thread here is aimed to provide informations and a place to discuss those changes in the Gentoo Forums.
I hope you'll all like the changes we made to the PHP support, and we're awaiting your reactions, be they constructive criticism, comments, ideas for improvement or simple questions. Please also always check our Wiki to see if the information/answer you're seeking isn't already available there, thanks.

Stuart Herbert wrote:

Hi,

The PHP Herd is pleased to announce that it has added new packages to
Portage which will allow Gentoo to provide stable PHP4 and PHP5 packages
on the same box at the same time. These packages have come from the
successful PHP Overlay [1].

At the heart of these packages is the new dev-lang/php package (which
will replace the existing dev-php/php, dev-php/php-cgi, and
dev-php/mod_php packages), and the new dev-php4 and dev-php5 categories
which allow us to provide, and support, PHP extensions and frameworks
that are specific to each version of PHP.

These changes also leave us well-placed for the next major release of
PHP (possibly called PHP-6), which upstream are currently brewing.

We hope to move these packages to ~arch (on architectures that the PHP
Herd supports) on Thursday 8th September, as part of our migration plans
[2]. If you find any problems with the packages, please file bugs in
Bugzilla as normal.

We are aiming to remove the old dev-php/php-4* et al packages on 8th
January 2006; support for non-security issues will cease two months
earlier on 8th October 2005. The older dev-php/php-5* et al packages
have been removed today; anyone still using these packages should move
across to the new dev-lang/php package.

Support for other architectures will follow as and when other arch teams
can resource it; you can follow the progress in [3], and provide
feedback to help the arch teams assess the stability of these packages.

The PHP Overlay will continue to be the place where the PHP Herd does
most of its development and testing. You'll find more packages in the
Overlay than in Portage, and new versions of packages will be tested in
the Overlay first.